Clinical Question

Is the use of prophylactic antibiotics for mammalian bites effective in preventing wound infections?

Conclusion

Antibiotic prophylaxis after human bites and bites of the hand may decrease the risk of wound infection but further evidence is needed. No evidence shows effectiveness in the use of antibiotic prophylaxis after cat or dog bites.

Major Points

Prophylactic antibiotics were associated with statistically significant reduction of infection rate for the following type of bites:

bites by humans

bites located on the hand (NNT=4)

Prophylactic antibiotics did not appear to reduce rate of infection after bites by cats or dogs

Prevention of tetanus/rabies, together with adequate cleansing of the wounds are the cornerstone of infection prevention in mammalian bites. In select patients, with concerning bite location (e.g. hand) and type of mammal (e.g. human) prophylactic antibiotics may be beneficial

Subgroup analysis

Animal Species

Human bites: 0% (0/33) for antibiotic group vs. the control group 47% (7/15) (OR 0.02, 95% CI 0.00 to 0.33)

Dog Bites: 4% (10/225) for antibiotic group vs to 5.5% (13/238) for control

Cat Bites: 0% (0/5) for antibiotic group vs 67% (4/6) for control (included only 1 study with 11 patients)

Wound Type

Wound type did not significantly influence the effect of prophylactic antibiotics

Punctures: 7% (1/14) vs 31% (5/16)

Lacerations: 3% (2/63) vs 6% (4/66)

Avulsions: 5% (2/41) vs 3% (1/30)

Location of Wound

Significant reduction of infection rate was seen in hand bites

Hand: 2% in antibiotic group vs 28% in control (OR 0.10, NNT=4)

Trunk: Infection occurred in only 1 patient in control group, none in antibiotic group

Head/Neck: Infection occurred in only 1 patient in control group, none in antibiotic group

Arms: No infection recorded in either group

Criticisms & Further Discussion

Significant heterogeneity was observed in the meta-analysis

Small number of overall amount of patients, therefore cannot rule out possible beneficial effect of prophylactic antibiotics that was not observed due to study size

The antibiotics used in the studies varied significantly, and therefore the effect of antibiotic prophylaxis may have been reduced by inappropriate antibiotic choice [1]

Further RCT's are indicated to evaluate the true effectiveness of antibiotic prophylaxis for mammalian bites and specific subgroups which may benefit

Beyond antibiotics, the additional question that needs to be answered is primary vs. secondary closure of the wound. Traditional belief has been that while primary closure improves cosmesis, these wounds are particularly dirty and closure may increase infection rate. Recent studies and reviews have challenged this belief, particularly for wounds closed within 8 hours and given ABX's [2]

Funding

Funding for Cochrane Review's come from internal sources within the Cochrane Collaboration, primarily from proceeds from The Cochrane Library.